Proximal discovery is the ability for devices to passively and continuously search for relevant value in physical proximity thereof. For example, a device can utilize location technologies to search for and detect other devices in proximity that utilize the same application. Presently, BLUETOOTH, WI-FI, radio frequency identification (“RFID”), and other like technologies are used for proximal discovery. These technologies exhibit several disadvantages. For example, these technologies offer low capacity, require the expense of technology-specific hardware (e.g., dedicated BLUETOOTH, WI-FI, and/or RFID hardware components), and reduce device battery life, among other disadvantages.
Long-Term Evolution (“LTE”) DIRECT is a device-to-device communications technology that utilizes licensed LTE spectrum for proximal discovery. LTE DIRECT is available from QUALCOMM TECHNOLOGIES, INC. and leverages the global LTE standard as part of Third Generation Partnership Project (“3GPP”) Release 12. LTE DIRECT also can be used on unlicensed spectrum. LTE DIRECT is superior to the competing technologies described above in many ways. LTE DIRECT offers increased battery life, greater radio frequency (“RF”) coverage, user scalability, and LTE world-wide adoption. LTE DIRECT, however, has several drawbacks, including granularity and accuracy of location data. In particular, LTE DIRECT has a major drawback in that two or more devices in “proximity” is approximated by the devices being in the same cell tower sector, resulting in a relatively large area of approximately 500 meters of proximity. This is a typical value but is impacted by LTE RF sector size, RF propagation, timing, and other factors. This drawback limits the practical use cases and commercialization of LTE DIRECT to use cases that do not require high location accuracy, especially those use cases that require more granularity than 500 meters.
LTE DIRECT utilizes LTE proximity and public safety standards defined in 3GPP Release 12 to work with an LTE DIRECT-defined expression server that facilitates proximal discovery of users. “Users” in LTE DIRECT are LTE-based devices and applications with common interests. The interests are represented in signals called “expressions.” Expressions are sent to and translated by the expression server. Expressions can be private and discreet, such as those targeted securely for certain audiences only. Expressions can be public, such as those transmitted so that any application can receive them. Public expressions are a common language available to any application to discover each other. Public expressions exponentially expand the field of value for proximity applications.